Kinescope photoelectrophoretic imaging method and systems

ABSTRACT

Black and white and color kinescopes are used as the exposure mechanism in a photoelectrophoretic imaging system. Images are formed on the face plate of a kinescope as a roller electrode travels over the face plate.

United States Patent Gundlach [4 May 16, 1972 [54] KINESCOPE 1 Referenm Cited IMAGING UNITED STATES PATENTS 3,427,242 2/1969 Mihajlov ..204/181 [72] Inventor: Robert W. Gundlach, Victor, NY. 3,451,812 6/1969 Tamura ....1 17/336 CM [73] Assigneez Xerox Corporation Rochester, NY 3,554,889 1/1971 Hyman et a1 ..204/181 [22] Filed: Feb. 2, 1970 Primary Examiner-Howard S. Williams [21] A 1 No 7 933 Attorney-James J. Ralabate, David C. Petre and Michael H.

pp Shanahan [52] [1.8. CI ..204/181, 355/12, 355/17, [57] ABSTRACT [51 1 Int CL Bolk 5/00 Black and white and color kinescopes are used as the exposure 58 Field of sea hi;.1.IZIIIZIZIII:....2o4/1 8i l81 C 300 mechanism in a Pmmelecmphmfic imaging System Images 7' V1 DEO DETECTOR are formed on the face plate of a kinescope as a roller electrode travels over the face plate.

19 Claims, 4 Drawing Figures POWER SUPPLY DEFLECTION Pa tented May 16, 1972 3,663,396 2 Sheets-Sheet 1 8M POWER 1 SUPPLY A 4 5 /5 I 9 DETECTOR AMP. 2 /a H&V" DEFLECTION I FIG. 1

POWER F SUPPLY 55 W as 0 GR sou 67 RB X 6 0 r 52' G 57 Q @i c;

58 I R B a? 59 FIG. 2

INVENTOR.

ROBERT W. GUNDLACH Patented May 16, 1972 .2 Sheets-Sheet 2 FIG. 3

MODULATOR SCANY& SYNC {CAME-RA H &V DEFLECTION VIDEO DETECTOR FIG. 4

KINESCOPE PHOTOELECTROPHORETIC IMAGING METHOD AND SYSTEMS BACKGROUND OF THE INVENTION ing positive or negative images on either the-injecting or blocking electrodes by having the CRT invert or not invert the image represented by the video signals. Color images are produced by using a color generating CRT and a polychromatic ink. The color CRT is particularly versatile because the video signals can be altered to match the spectrum of the radiation to the photosensitive and reflective characteristics of the ink. The video signals for the monochromatic and the electric field and is exposed to a light image through one of the electrodes which is at least partially transparent. According to one theory, particles attracted to the injecting electrode by the electric field exchange charge with the injecting electrode when exposed to light and migrate under the influence of the field through the liquid carrier to the blocking electrode. As a result of the migration, positive and negative images are formed on the two electrodes. The blocking electrode is covered with a dielectric material to prevent charge exchange with the particles and thereby prevent the particles from oscillating back and forth between the two electrodes.

The photoelectrophoretic imaging process is either monochromatic or polychromatic depending upon whether the light sensitive particles within the liquid carrier are responsive to the same or different portions of the light spectrum. A full color polychromatic system is obtained, for example, by using cyan, magenta and yellow colored particles which are responsive to red, green and blue light respectively. An extensive and detailed description of the photoelectrophoretic process is found in US. Pat. Nos. 3,384,565 and 3,384,488 to Tulagin and Carreira, 3,383,993 to Yeh and 3,384,565 to Clark and the disclosures of these patents are expressly incorporated by reference into the present disclosure.

The present photoelectrophoretic imaging methods and apparatus depart from prior systems by employing novel mechanisms for exposing the photoelectrophoretic ink to activating radiation. Accordingly, it is an object of the present invention to devise novel and improved photoelectrophoretic imaging methods and apparatus. Specifically, it is an object of this invention to incorporate a cathode ray tube (CRT) into a photoelectrophoretic imaging system. I

Another object of the present invention is to locate the illumination source generating the activating electromagnetic radiation immediately adjacent the transparent electrode through which the photoelectrophoretic ink is exposed.

Still another object of this invention is to devise methods and means for employing a three gun shadow mask color kinescope as a polychromatic illumination source in a photoelectrophoretic imaging system.

Even a further object of the present invention is to match the colors of a light source to the response of the photosensitive pigments or particles of a photoelectrophoretic ink to give color correction in a single simultaneous exposure and development step.

It is also an object of the invention to develop means for producing photoelectrophoretic images at remote locations from an original.

In the present imaging systems, a cathode ray tube is the illumination source generating the radiation to which the photoelectrophoretic ink is exposed. In addition, the face plate of the CRT serves as one of the system electrodes thereby eliminating mirrors and lenses from the system. The exposure takes place in a nip formed between the CRT face plate and a roller electrode that travels over the face plate. The light image created by a CRT is readily made a positive or negative (in the classic photographic sense) by simple electrical manipulation of the video signal representative of the image. Consequently, the present system is capable of producpolychromatic imaging systems are generated by television camerasThese video signals can be coupled directlyto a CRT such as in a closed circuit television network, stored on a magnetic tape or transmitted by radio or cable to a remotely located CRT.

DESCRIPTION OF THE DRAWINGS The foregoing and other objects of the present invention will be apparent from a further reading of the present description and from the drawings which are:

FIG. 1 is a schematic of a photoelectrophoretic imaging system employing a monochromatic cathode ray tube as the system exposure mechanism.

FIG. 2 is a schematic of a photoelectrophoretic imaging system employing a three gun shadow mask color kinescope as the exposure mechanism.

FIG. 3 is a schematic of a segment of a color kinescope target of red, blue and green phosphors with projections of the holes in the kinescope shadow mask overlaying the phosphors.

FIG. 4 is a schematic of a photoelectrophoretic imaging system having a CRT exposure mechanism coupled to a television camera by a conventional radio communication network.

DESCRIPTION OF THE INVENTION The injecting electrode of the present photoelectrophoretic imaging systems includes the layer 1 (FIG. 1) of transparent conductive material such as tin oxide deposited on a glass substrate 2. The transparent glass substrate 2 is the faceplate of cathode ray tube (CRT) 3 which is the exposure means for the system. The face plate is flat, i.e., a plane, but may be cylindrically shaped to accommodate structural considerations of the CRT. Also, the flat or cylindrical shape of the face plate enables the nip to be conveniently formed between the tin oxide layer 1 and the roller member 4. The roller is the blocking electrode for the system being of conventional design having an outer electrically insulating layer 6 and an inner electrically conducting core 7. The nip is the area defining the interface between the two electrodes whether they are in contact or separated by a photoelectrophoretic ink 5. The functional roles of the face plate electrode and the roller electrode can be interchanged such that an insulating material on the face plate abutts a conductive material on the roller. However, it is normally preferred that the transparent electrode be an efficient charge exchange device, i.e. an injecting electrode, and in the present system, it is preferred that the face plate be transparent rather than the roller.

The tin oxide layer 2 (hereafter called the face plate electrode) and the roller electrode 4 are coupled to power supply 8 to apply a voltage gradient between the electrodes. The voltage gradient includes a voltage potential difference of generally 3,000-4,000 volts and establishes the electric field that effects ink particle migration.

A photoelectrophoretic ink 5 is applied between the electrodes normally by coating either the face plate or the rollerwith the ink. The ink may be monochromatic or polychromatic, but if it is polychromatic, CRT 3 is replaced by a color producing kinescope discussed in more detail later. Complementary photoelectrophoretic images are formed on the face plate and roller as the roller moves over the CRT face plate (or the CRT is moved relative to the roller). The images are formed in a line by fashion from the ink in the vicinity of the nip exposed to activating electromagnetic radiation generated by CRT 3 and subjected to the electric field generated by power supply 8.

The photoelectrophoretic ink image formed on the face plate is a positive image having light areas representing corresponding light areas in the CRT created image. The ink image formed on the roller is a negative image having light areas representing corresponding dark areas in the CRT created image. The light image generated by a CRT is readily inverted from a positive image to a negative image by complementing the electrical video signals that represent the image. For example, if a voltage range from to volts represents CRT illuminations ranging from near black to near white, a positive image is generated from video signals having amplitudes near 0 volts to represent the dark area of an image and near 10 volts to represent the light areas of an image. The image represented by these video signals is easily inverted by referencing the video signals to l0 volts and by inverting the v resultant signal to correct the polarity. The image inversion ability of a CRT enables positive ink images to be produced on either the face plate 2 or the roller by selecting the proper number of image inversions. For example, video signals representing a positive image of an original are electrically altered to have the CRT create a negative light image of the original. This negative light image in turn results in the production of a negative ink image on the face plate and a positive ink image on the roller by reason of the normal inversion that occurs in the above described photoelectrophoretic imaging process.

The activating electromagnetic radiation to which the ink is exposed is generated by exciting the CRT phosphor layer 9 with a stream of electrons l0 emitted by the electron gun 11 (FIG. 1). The stream of electrons, i.e. electron beam, produces substantially a point illumination source on the phosphor layer which is hereafter referred to as the scanning spot. The reflection layer 12 of aluminum adjacent the phosphor layer is commonly included in a CRT and is coupled to a voltage potential to attract the electron beam. (The polarity of the voltages coupled to the CRT face plate and roller may be selected so as not to interfere adversely with the acceleration of the electron beam toward the phosphor). The aluminum layer is permeable to the electron beam but reflects the radiation emitted by the phosphor outward through the face plate. The size, shape, duration and intensity of the scanning spot are varied to change the quantity of radiation to which the ink is exposed. The foregoing variations to the scanning spot are made by controlling the electron beam by well known apparatus and techniques. The photosensitive ink particles opposite the scanning spot are caused to migrate from the face plate to the roller under the influence of the field in quantities proportional to the intensity of the scanning spot. A two dimensional image is formed from the scanning spot by sweeping the spot along the nip to form a linear element and then by moving the nip, i.e. the roller, over the CRT face plate. The intensity of the spot is varied during its travel in accordance with the intensity of corresponding points or spots on an original.

The rotational and transitional velocities of the roller electrode are normally constant and are selected to establish a zero relative velocity between points on the roller and the CRT face plate. The substantially zero relative velocity prevents the ink images from being smeared and otherwise adversely affected by reason of the relative movement between the electrodes.

A particularly unique and advantageous feature of this invention is that the light emitting phosphor is immediately adjacent the transparent electrode of the imaging system. This location of the light source allows the activating radiation to pass directly from the source to the ink without being attenuated by mirrors or lenses. The thickness of the transparent electrode, primarily the glass face plate 2, should be considered in regard to image resolution. The scanning spot radiation spreads, i.e. defocuses, as it passes from the phosphor 9 to the ink 5 through the glass face plate 2 and tin oxide layer 1. A controlling factor of the face plate thickness is the fact that the plate must be strong enough to withstand the pressure gradient across it due to the near vacuum inside a CRT. If the face plate thickness is such as to result in unacceptable defocusing, a fiber optic face plate is substituted for the glass face plate 2. A fiber optic plate is composed of a plurality of optical fibers having diameters generally in the order of magnitude of the scanning spot diameter and length generally in the order of the desired plate thickness. The plate receives structural strength by binding the fibers together with an appropriate cement or hinder material. FIG. 3 is a schematic of a typical color kinescope phosphor target discussed elsewhere but it is also illustrative of a plan view of a fiber optic face plate. The phosphor dots 58, 59 and 60 represent the ends of the plurality of parallel arranged optical fibers and the interstices between the dots represent the area filled with the binder material.

The electron beam producing the scanning spot is swept across the width of the face plate opposite the nip and is moved synchronously with the roller as it travels over the face plate. The deflection circuit 13 (of conventional design) is coupled to the CRT deflection yoke 14' and controls the deflection of the electron beam across the width and along the length of the face plate. The intensity of the electron beam is controlled by applying appropriate voltages (the video signal) to the gun cathode 15 to regulate the density of electrons in the beam. Appropriate control over beam focusing, astigmatism, pincushion, etc., are provided by conventional apparatus and techniques.

The speed of the beam along the nip (controlled by deflection circuit 13) is made many times greater than the translational speed of the roller electrode so that the nip is substantially stationary relative to the moving light source. (The speed of the scanning spot may be substantially slower than the speed of a scanning spot in current commercial television receivers, for example, because of the sensitivity of some photoelectrophoretic inks.) At the end of each sweep along the nip, the electron beam is blanked to provide time for the roller to move some finite distance, e.g. the diameter of the scanning spot, before the next scan. The deflection circuit 13 deflects the beam vertically a sufficient distance to position the scanning spot opposite the new nip location.

FIG. 4 illustrates a block diagram of an imaging system that includes a typical television system modified to incorporate the foregoing CRT photoelectrophoretic imaging apparatus. The television camera 16, e.g.-an image orthicon tube, electrically records a scene or original 17 projected to it by lens 18. The electrically recorded image is scanned point by point (spot by spot) in a systematic manner to produce an electrical video signal whose instantaneous amplitude represents the intensity of an incremental area on the original. The scanning and synchronizing circuit 19 controls the scanning operation of the camera and adds information to the video signal at amplifier 20 to properly identify each-signal amplitude with a corresponding incremental area on the original. The synchronized video signal of amplifier 20 is applied to the monitor CRT 21 via proper scan and video control circuitry 22. An operator normally uses the image displayed on Monitor 21 to ensure himself that the proper video signals are being produced by the camera 16. The loop between the camera and monitor CRT comprises a closed circuit television network.

29 and amplifier 30 to the cathode of CRT 32. The video signal varies the intensity of the electron beam and consequently, the intensity of the scanning spot. In the meantime, the synchronization signal transmitted with the video signal is fed to the horizontal and vertical deflection circuit 33 which is coupled to the deflection coil or yoke of CRT 32 to move the scanning spot in the same pattern that the camera 16 scans the original 17.

The scanning pattern or raster used by camera 16 and CRTs 21 and 32 is selected to conform to the needs of the photoelectrophoretic imaging system that includes the CRT 32, roller electrode 35 and power supply 36. That is, a horizontal line on original '17 is scanned, by the camera at a rate and for a number of times needed to form an image from photoelectrophoretic ink between a tin oxide layer on the face plate of CRT 32 and the roller 35. The linear scan 'of the original is advanced vertically at the rate that roller 35 moves over the face plate of CRT 32.

The image formed from the photoelectrophoretic ink on the face plate of CRT 32 is commonly transferred to a record member by means that includes a transfer roller used to establish an electrical field having a polarity opposite that used in forming the image. The surfaces of the CRT face plate and the roller electrode are cleaned and the roller is moved back to a starting position in preparation for the formation of additional photoelectrophoretic ink images.

The video signals and accompanying synchronization signals generated at camera 16 can be recorded on magnetic tape. The recorded signals can be replayed directly to the CRT 32. (and associated circuitry) rather than be transmitted via the radio transmission link represented by antennae 26 and 27. Furthermore, the video signals can be transmitted over a telephone communication network rather than a radio network. Also, if the monitor CRT 21 is combined with a tin oxide layer, roller electrode, power supply and photoelectrophoretic ink, images can be made with it without using the communication network.

Color or polychromatic images are produced by the present invention by substituting a color generating CRT for the monochromatic CRTs 3, 21 or 32. An example of a polychromatic CRT is the three gun shadow mask kinescope currently widely used in home television receivers. A segment of a shadow mask kinescope is illustrated in FIG. 2. The three electron guns of the kinescope (not shown) are positioned near the apexes of an equilateral triangle 50 and the electron beams 51, 52 and 53 emitted by the guns are accelerated toward the shadow mask 54. and target 55. The target includes a plurality of incremental areas or trios 57 composed of red 58, blue 59 and green 50 phosphors. The phosphors are adjacent the transparent glass face plate 62 which has the transparent layer ofconductive material 63, e.g. tin oxide, carried on its surface opposite the phosphors. A photoelectrophoretic ink 64, preferably. polychromatic, is shown coated over the tin oxide layer 63. Roller electrode 65 is substantially the same as roller 4 and is'the systemblocking electrode which forms a nip with the transparent conductive layer 63.

The shadow mask 54 is an electron absorbent plate having a plurality of holes 67. Eachhole in the shadow mask is aligned with a trio 57 such that a projection 68 (F IG. 3) of a hole onto a trio overlays substantially equal areas of the three phosphors. The red, blue and green phosphors are arranged in equilateral (all angles being 60) triangles having a side of length a. Each hole 67 and its projection is aligned over the center of the, equilateral triangle formed by the three phosphors of a trio 57.

V The electron beams 51-53 emitted by the kinescope guns are made to converge at the holes 67 in the shadow mask byv appropriate focusing means. As the three beams pass through a hole, they diverge with one striking the red phosphor, another the blue phosphor and the third, the green phosphor. By modulating the. intensity of the three beams 51-53 the brightness and color of each trio 57 is made to simulate the brightness and color of an incremental area on an original. All the trios 57 on the CRT target, when viewed from the proper distances, compose a faithful reproduction of the original. That is to say, the human eye integrates the plurality of dots or trios and interprets them as a solid area. The same effect is at work in the present imaging system, however, in the present case, the viewers eye integrates incremental areas of photoelectrophoretic ink rather than phosphor trios.

Images are formed with a color kinescope in a manner similar to image formation with CRTs 3, 21 or 32. Three video signals representing red, green and blue intensities are generated and applied by appropriate well known means. to the cathodes of the three electron guns of the color kinescope. The radiation emitted by the red phosphor of a trio 57 activates cyan ink particles laying opposite the excited phosphor causing them to migrate from the face plate to the roller under the influence of the field established by the power supply 70. Likewise, the radiation emitted by the green and blue phosphors of a trio activate magenta and yellow ink particles, respectively. Some lateral spread, i.e. defocusing, of the light emitted by each phosphor, at least over the area of its trio, is desirable. The reason being that a reflection image composed of adjacent yellow, magenta and cyan pigments is capable of producing only a medium grey when attempting to simulate white. Allowing the radiation from a phosphor to effect all the ink in the area of a trio enables the combination of pigments in the trio to be adjusted to simulate for the eye of a viewer a color closer to white. The result is that the ink image has a brightness range from near white to black rather than from medium grey to black. The three electron beams 51-53 move from hole to hole (i.e. holes 67 in mask 54) along the nip formed between the transparent conductive layer 64 and roller 65. A two dimensional image is formed over the entire surface of target 55 as the roller electrode 65 moves over the target. The resultant image is composed of incremental areas or trios of cyan, magenta and yellow ink particles which, when viewed from the proper distance, appear as a solid area having color and brightness variations corresponding to an original. A complementary color image is formed on the roller electrode.

The foregoing polychromatic imaging system is based on the assumption that the cyan, magenta and yellow ink particles (or other polychromatic pigment combinations) are mixed together such that randomly selected incremental volumes of ink contain similar proportions of the three pigments. This assumption is readily proven valid by appropriate statistical analysis of randomly mixed objects in a fixed volume.

The CRT light source in a color or polychromatic imaging system provides a color correction capability. The video signals representative of a multi-color image may be altered or initially constructed to have the CRT generate colors that effect a particular response from the photoelectrophoretic ink. That is, the colors of a photoelectrophoretic image can be corrected to more nearly match the colors of an original by having the CRT distort the color of the original. The color is distorted so as to match the photosensitive response of the' various colored ink particles.

The distortion of the three video signals effecting color correction is performed by conventional circuitry at any of several appropriate locations in a particular color television system. Functionally, the color correction circuitry examines the three video signals to determine the intensity or brightness of the color they represent and changes the intensity in accordance with conventional color correction techniques. For example, in a color television system using signal amplitude to represent intensity, the amplitudes of the blue and green video signals are increased where the amplitude of the red video signal is low and the amplitude of the blue signal is increased where the amplitude of the green signal is low. The changes to the video signals compensate for the non-ideal response of yellow, magentaand cyan pigments to the blue, green and red electromagnetic radiation.

, The present invention is not limited to the foregoing described embodiments, but is intended to include modifications that are logical extensions and/or variations of it. For example, the electric field applied between the roller and CRT face plate electrodes may be modulated rather than the intensity of the electron beam. Other similar modifications and variations within the scope of the present invention will occur to those skilled in the imaging art.

What is claimed is:

l. Photoelectrophoretic imaging apparatus comprising a cathode ray tube having a transparent electrode adjacent its face plate and a second electrode adjacent the transparent electrode, and

means for applying a photoelectrophoretic ink between said electrodes to form images from ink exposed to activating electromagnetic radiation generated by said cathode ray tube and subjected to an electric field established by voltage gradient applied between said electrodes.

2. The apparatus of claim 1 wherein said cathode ray tube includes means for generating polychromatic electromagnetic radiation.

3. The apparatus of claim 1 wherein said cathode ray tube includes a three gun shadow mask three phosphor coated cathode ray tube.

4. The apparatus of claim 1 wherein said cathode ray tube includes a cylindrically shaped face plate.

5. The apparatus of claim 1 further including means for electrically inverting video signals representative of an image applied to said cathode ray tube to effect an inversion of the image represented by said video signals.

6. The apparatus of claim 1 further including means for generating electrical video signals representative of an image to be reproduced and means for applying said video signals to the cathode ray tube.

7. The apparatus of claim 1 wherein said transparent electrode includes a layer of conductive material coated on the face of said tube.

8. The apparatus of claim 1 wherein the face plate of said cathode ray tube is comprised of optical fibers for transmitting the radiation generated by said tube to an ink.

9. The apparatus of claim 1 wherein said second electrode includes a roller member supported for relative movement with said tube and transparent electrode forming a nip with the transparent electrode in which image formation occurs.

10. The apparatus of claim 9 further including means for synchronizing the generation of electromagnetic radiation with the relative movement of the roller member and transparent electrode.

11. A photoelectrophoretic imaging method comprising applying photoelectrophoretic ink between a transparent electrode carried on the face of a cathode ray tube and a g 8 second electrode, and

modulating and sweeping the tube scanning beam to generate activating electromagnetic radiation in imagewise configuration to form images from ink exposed to the radiation generated by the tube and subjected to electric field established by a voltage gradient applied between the electrodes.

12. The method of claim 11 wherein said cathode ray tube includes means for generating polychromatic activating electromagnetic radiation.

13. The method of claim 12 wherein said second electrode includes a roller member supported to form a nip with the transparent electrode and for travel over at least a portion of the face of said tube.

14. A photoelectrophoretic imaging system comprising means. to generate video signals representative of an image to be reproduced,

a cathode ray tube capable of producing electromagnetic radiation in imagewise configuration in response to said video signals, and

first and second electrodes one of which is transparent to the electromagnetic radiation generated by said tube to permit exposure of photoelectrophoretic ink on said electrodes whereby images are formed from ink exposed to radiation and subjected to an electric field established between the electrodes.

15. The system of claim 14 wherein said means to generate said video signals and said cathode ray tube comprise a closed circuit television network.

16. The system of claim 14 further including means for recording said video signals and for coupling said recorded signals to said cathode ray tube.

17. The system of claim 14 wherein said means for generating said video signals is coupled to said cathode ray tube by a radio communication network.

18. The system of claim 14 wherein said means for generating video signals is coupled to said cathode ray tube by a telephone communications network.

19. The system of claim 14 wherein said tube produces polychromatic electromagnetic radiation in response to said video signals and further including circuit means for changing said video signals to compensate for the non-ideal response of ink pigments to electromagnetic radiation. 

2. The apparatus of claim 1 wherein said cathode ray tube includes means for generating polychromatic electromagnetic radiation.
 3. The apparatus of claim 1 wherein said cathode ray tube includes a three gun shadow mask three phosphor coated cathode ray tube.
 4. The apparatus of claim 1 wherein said cathode ray tube includes a cylindrically shaped face plate.
 5. The apparatus of claim 1 further including means for electrically inverting video signals representative of an image applied to said cathode ray tube to effect an inversion of the image represented by said video signals.
 6. The apparatus of claim 1 further including means for generating electrical video signals representative of an image to be reproduced and means for applying said video signals to the cathode ray tube.
 7. The apparatus of claim 1 wherein said transparent electrode includes a layer of conductive material coated on the face of said tube.
 8. The apparatus of claim 1 wherein the face plate of said cathode ray tube is comprised of optical fibers for transmitting the radiation generated by said tube to an ink.
 9. The apparatus of claim 1 wherein said second electrode includes a roller member supported for relative movement with said tube and transparent electrode forming a nip with the transparent electrode in which image formation occurs.
 10. The apparatus of claim 9 further including means for synchronizing the generation of electromagnetic radiation with the relative movement of the roller member and transparent electrode.
 11. A photoelectrophoretic imaging method comprising applying photoelectrophoretic ink between a transparent electrode carried on the face of a cathode ray tube and a second electrode, and modulating and sweeping the tube scanning beam to generate activating electromagnetic radiation in imagewise configuration to form images from ink exposed to the radiation generated by the tube and subjected to electric field established by a voltage gradient applied between the electrodes.
 12. The method of claim 11 wherein said cathode ray tube includes means for generating polychromatic activating electromagnetic radiation.
 13. The method of claim 12 wherein said second electrode includes a roller member supported to form a nip with the transparent electrode and for travel over at least a portion of the face of said tube.
 14. A photoelectrophoretic imaging system comprising means to generate video signals representative of an image to be reproduced, a cathode ray tube capable of producing electromagnetic radiation in imagewise configuration in response to said video signals, and first and second electrodes one of which is transparent to the electromagnetic radiation generated by said tube to permit exposure of photoelectrophoretic ink on said electrodes whereby images are formed from ink exposed to radiation and subjected to an electric field established between the electrodes.
 15. The system of claim 14 wherein said means to generate said video signals and said cathode ray tube comprise a closed circuit television network.
 16. The system of claim 14 further including means for recording said video signals and for coupling said recorded signals to said cathode ray tube.
 17. The system of claim 14 wherein said means for generating said video signals is coupled to said cathode ray tube by a radio communication network.
 18. The system of claim 14 wherein said means for generating video signals is coupled to said cathode ray tube by a telephone communications network.
 19. The system of claim 14 wherein said tube produces polychromatic electromagnetic radiation in response to said video signals and further including circuit means for changing said video signals to compensate for the non-ideal response of ink pigments to electromagnetic radiation. 